Two things that do not go together, although I suspect Heinlein might have enjoyed those books.

I just finished rereading The Door Into Summer, which was the first Heinlein adult novel I'd ever read, and that at the age of eleven, thirty years ago.

SF is not a crystal ball and the writers are not seerss. Occasionally, the writers guess right - Asimov with pocket calculators, Clarke with satellite communication, Heinlein with water beds - but most of the time, they can only extroplate from things they have at the time.

SF is a mirror of the times in which it was writing. TDIS is perhaps one of the best examples. It was written in 1956, and set in two time periods - 1970 and 2001. We didn't spend much time in 1970, but socially it was still 1956 - a woman did not live openly with a man to whom she was not married, which was already happening at that point. A woman did not run a company and certainly didn't do technical things. (Something I found interesting because the woman in question had some highly technical skills, especially with an electric typewriter.) And there was no sense that women would ever use drafting tools (which is confusing, because interior and fashion design used such things, and were done by women.)

The technological/scientific advances were also - well, not as they had gone. His big "inventions" - cold sleep, which never happened, and "Thorsen tubes" for memory storage. I'd have to check, but that sounds right for 1956. I'm nos so sure about 1970, and clearly not since then. Still, a reasonable extrapolation.

(He did manage to invent the Roomba, though. :))

It was the 2001 cultural stuff that kept tripping me up - the first thing the doctor does upon awakening the protagonist from cold sleep was to offer him a (self-lighting)cigarette on the grounds that it couldn't hurt him. The fact that when he used the word "kink" (from context, equaling the f-word) in front of a lady, her husband nearly punched him in the mouth. That there was still the assumption that women would not be interested in technical things at all, and would go all, "Not my silly brain."

And then there was the squick factor. Now, this is purely personal, but it bothered me in 1974 and it bothers me now. In the story, the protagonist (Danny) makes friends with his partner/best friend's ten year old stepdaughter Ricky. They share a lot in common, given he's about twenty years older than she is, including a love of his cat. He seeks her out in the future, and then goes back to the past and ensures it happening, including agreeing to marry her. The day she comes out of cold sleep, at the physical age of twenty-one, he does so. Which means that, however beautiful she was an adult, he essentially married a woman he'd last seen as prepubescent and whom he probably thought of in that way. And it means that she chose to give up any other possible options for her life. And it just squicks me.

I thought he'd merely correctly predicted the usage of the word meaning "perversion". Of course that assumed that in 2001 anybody would still feel inhibited about discussing either perversion by name or by euphemism.

The "squick" thing -- agreed. There is however a running thread in that regard. I can't read too deeply into "Have Spacesuit, Will Travel" without beginning to worry about teenaged Kip's relationship with pre-pubescent PeeWee.

That's what I thought, until Belle Gentry Schultz used it perjoratively. "We were kinking cheated."

Let's not forget Dora. Then again, not so long ago, I realized Time Enough for Love is a long and disjointed rationalization of incest - all of the stories except for "The Man Who Was Too Lazy to Fail" on that subject, culminating in Woody and his mother.

I'm not so sure how unreasonable it is to base a relationship on knowing one of the people as a child.

There are lots of things that could go badly wrong with this scenario. A relationship between people of wildly different ages can have terrible power imbalances. The bit with the time machine and cold sleep evened that out, to a great degree. When they married, the ages were Dan, about 30, and Ricky, 21, which is not too extreme.

Not all relationships between people of widely different ages involve condescension. Of course, you may not have experienced this.

This is partly from my pop psych reading, which was quite extensive years ago when I was getting a divorce, but a couple of authors had models with variations on the "inner child." While I found much of that to be junk, the idea that an important part of your personality crystallizes (pardon the metaphor) between the ages of 3 and 5 and carries on essentially unchanged really resonated with me. I became who I essentially am at about the age of four and have a continuous memory track since then. I've learned stuff and made necessary changes, and of course more of my brain came online at various developmental stages (try to think when your brain is under construction; it's no wonder teenagers seem nuts), but even if it makes me a case of arrested development, I'm still that kid on some level.

If the 10-year-old grows up to a 20-year-old, normally the 30-year-old becomes a 40-year-old during those 10 years, and we look a bit askance at that age difference, but what we would really condemn is a sexual relationship between the 10-year-old and the 30-year-old, and no such thing was even implied. Dan didn't experience those extra 10 years, so the age gap narrowed.

Anyway, at the level of intimate relations, I think that my interior 5-year-old likes hanging out with my wife's interior 5-year-old. Not that we act like 5-year-olds (some of those behaviors we can really do without), but there is still an element of that early playfulness, which modern industrial society tries to iron out of us, that contributes to who we are when we drop our barriers. A lot of stuff gets added later, and professional relationships really depend on the stuff that you learn in college or on the job, but the connection you have with your really close friends is more visceral.

As portrayed, it worked for me. It wouldn't be for everyone, but it would work for some. Some people have a strong sense of who they are early, and others find out later. And don't tell me 8-year-olds don't have an inkling of their future sexual identities.